Abstract
Individuals with depression
experience more negative imagery and less vivid positive imagery, and
the
late
positive potential (LPP) is
considered as a viable biomarker for negative attentional and memory
biases in depression; however, the
LPP response to emotional imagery in
depressed individuals remains unclear. This study aims to investigate
neural response to emotional imagery in depressed individuals. ERPs were
recorded from 40 depressed participants and 44 healthy controls during
the encoding-imagery task. Depressed participants scored significantly
lower in the valence rating of sad and neutral imagery compared to
healthy participants. Importantly, the LPP amplitudes to sad imagery in
depressed participants were significantly larger than healthy controls,
particularly in the middle (800-1,400 ms) and late time
windows(1,400-2,000 ms). Furthermore, depressed individuals exhibited
significantly higher LPP amplitudes for sad imagery
compared to happy imagery, whereas
healthy participants showed the opposite pattern.
The present study provides evidence
that depressed individuals display abnormal electrophysiological
reactivity to sad imagery, which offers a new perspective for
understanding the mechanisms
underlying depression.
Keywords: Depressed individuals, healthy controls,
event-related potentials (ERPs), late positive potential (LPP), and
emotional imagery
1.Introduction
Individuals with
depression
experience more intrusive negative imagery and less vivid positive
imagery (Holmes et al., 2016; Weßlau
& Steil, 2014). Abnormal emotional imagery may amplify other
maladaptive processes in depression, and play an important role in the
maintenance and development of depression (Holmes et al. 2009, 2016).
Examining imagery biases in
depression provides valuable insights into the mechanisms of this
disorder (LeMoult & Gotlib, 2019).
Moreover, depressed individuals have
mood-congruent internal mental representations or schemas (Beck, 1967),
and have been supported by numerous studies exploring the
neural response of depressed
individuals to external emotional stimuli
(Benau et al., 2019; Zhou et al.,
2021). However, emotional imagery, a mental representations of imagined
emotional events or stimuli, might more closely
mirror the experiences of
individuals with mood disorders (Bauer & MacNamara, 2021). Therefore,
exploring the neural correlates of emotional imagery in depressed
individuals may contribute to further understand the underlying
mechanisms of depression.
The late positive potential (LPP),
an event-related potential (ERP) beginning approximately 300-400 ms
following stimulus presentation at centroparietal electrodes, is a
reliable neural indicator to emotional stimuli(Hajcak & Foti, 2020;
Hajcak et al., 2010; Moran et al., 2013). The LPP is sensitive to
emotional stimuli and its amplitude elevated degree by emotional
material is related to subjective valence or intensity of emotional
stimuli (Hajcak et al., 2010). Furthermore, LPP might serve as a neural
marker of risk for affective psychopathology (Hajcak & Foti, 2020;
Moran et al., 2013), such as depression (Speed et al., 2016). For
example, greater pre-treatment LPPs to negative stimuli predicted
depression treatment outcome (Stange et al., 2017), and blunted LPP to
positive images predicted symptoms of depression (Sandre et al., 2019).
Larger LPP amplitudes to negative stimuli have been reported in adult
depression (Benau et al., 2019; Dainer-Best et al., 2017), in
adolescents with depression(Auerbach et al., 2015; Burkhouse et al.,
2017), in young adulthood with depressive symptoms (Xie et al., 2018),
as well as in children with maternal history of depression (Speed et
al., 2016). These studies suggested that LPP may be a viable biomarker
of negative processing biases in depression. However, there are
contradictory results. For example,
clinical or non-clinical depressed
individuals showed blunted LPP responses to
unpleasant images (Nikolin et al.,
2022), both pleasant and unpleasant images (Hill et al.,2019), and even
all emotional faces (Grunewald et al., 2019). Notably, depressed
participants exhibited enhanced LPP for self-referential negative words
(Auerbach et al., 2015; Dainer-Best
et al., 2017) and negative autobiographical memories(Speed et al.,
2020), suggesting that the LPP response to self-related or to internal
stimuli may be more stable.
Most previous laboratory studies have employed external stimuli such as
negative pictures and words to evoke negative emotion (Benau et al.,
2019; Nikolin et al., 2022). However, it is possible that imagined or
recalled negative scenarios are more closely to the experience of
individuals with mood disorders (Bauer & MacNamara, 2021). Several
studies have demonstrated the potential to elicit LPP responses to
emotional imagery in both healthy and clinical samples (Bauer &
MacNamara, 2021; MacNamara, 2018). For instance, healthy individuals
exhibited enhanced LPP responses to emotional imagery relative to
neutral imagery (MacNamara, 2018),
as well as larger LPP responses to positive imagery versus negative
imagery (Marmolejo-Ramos et al., 2015; Suess & Rahman, 2015). The
clinical findings indicated that depression was associated with reduced
LPP response to negative imagery
(Bauer & MacNamara, 2021). However, it should be noted that the
depressed participants in this clinical study presented complex comorbid
symptoms, including generalized
anxiety, social anxiety, and posttraumatic stress disorder. Furthermore,
the experimental materials only employed general negative imagery rather
than idiographic negative imagery. These studies suggested that the
heterogeneity of research methods and participant characteristics may
potentially affect the obtained results (Bauer & MacNamara, 2021; Benau
et al., 2019; Weinberg et al., 2016). Therefore, there is a need for
further investigation into the LPP response to emotional imagery in
individuals with depression.
Here, we first screened participants who met the diagnostic criteria for
depression, and then used pure
emotion images (happy, sad, and neutral scene images) as experimental
materials. To examine that emotional imagery can also cause the neural
response of depressed individuals like external emotional stimuli, this
study examined the LPP responses to emotional imagery. Based on
cognitive models of depression (Beck, 1967), we hypothesized that
depressed individuals would exhibit an enhanced LPP response to sad
imagery than healthy controls. Based on previous studies (Benau et al.,
2019; Dainer-Best et al., 2017), we expected that depressed individuals
would exhibit an enhanced LPP response to sad imagery relative to happy
and neutral imagery, whereas healthy controls would exhibit an enhanced
LPP response to happy imagery relative to sad and neutral imagery.
2.Methods
2.1. Participants
Participants were recruited from Jiangxi Normal University through
online advertisements. Inclusion criteria for the depressed group were
as follows: meeting the diagnostic criteria for current depressive
disorder, having a BDI-II score of 14 or higher, and an HDRS-17 score of
8 or higher for depressive symptoms experienced within the past 2 weeks.
Participants with bipolar disorder,
psychotic disorder, anxiety disorders, or current substance use disorder
were excluded. The healthy controls consisted of individuals with no
history of neurological or psychiatric illness, a BDI-II score of 13 or
lower, and an HDRS-17 score of 7 or lower.
Participants with BDI-II scores above 14 underwent initial screening
using Structured Clinical Interview for DSM-5 (SCID; First et al., 2015)
during the initial QQ voice interview. Those who met the criteria were
invited to the lab for an in-depth clinical interview. All participants
were right-handed, had normal or corrected normal vision, provided
informed consent prior to the experiment.
The Human Research Ethics Committee
of Jiangxi Normal University approved the study. EEG data were assessed
in 46 depressed participants and 46 healthy controls in the present
study. During the encoding-imagery task, 8 participants were excluded
due to excessive EEG drift (depression: n=5; control: n=2), or quitting
halfway due to discomfort (depression: n=1). Finally, the formal data
analysis included 40 depressed
participants and 44 healthy controls.
2.2. Measures
First, the current mood disorders were evaluated in all participants
with the SCID(First et al., 2015) by two PhDs in clinical psychology
supervised by a licensed psychiatrist. Furthermore, the current
depression severity and symptomatology were evaluated using the 17-item
version of the Hamilton Depression Rating Scale (HDRS-17; Hamilton,
1967) and the Chinese version of the Beck Depression Inventory-Second
Edition (BDI-II; Wang et al., 2011).
All participants were completed a questionnaire that was contained
demographic information and the Vividness of Visual Imagery
Questionnaire (VVIQ; Marks, 1973). Demographic characteristics and scale
scores of two groups are presented
in Table 1. Groups were matched age,
education level, and VVIQ score.
Table1. Demographic characteristics
and scale scores of depressed individuals and healthy controls